Build a configurable Online Store

For an example of a similar cart we're looking for, look at Dell's online shopping cart for configuring computers to purchase. We sell hardware along with a subscription base and offer support options. What i'm looking to do is have a cart where a customer can go "I want x amount of hardware" and then the cart will recommend the appropriate monthly subscription which they can change to be a higher subscription level or lower (depending on what they feel is required) or no monthly subscription at all - a description would need to be explained to the customer on each option. Then before checkout they can also add on support incident packages or bundles. When they select hardware, they have a choice of upgrading all their hardware to the next best thing or just parts of their order (for example they order 10 items and 3 are top of the line premium items and the other 7 are a mix of the cheapest and mid-tier items). Similar to the dell cart, i'd like the customer to focus on an individual page for configuration, once they have their hardware selected they click next and it can then go to the next page where they can focus just on that etc until they get to the end to submit their order. I'd then like the customer info registered into a database which can be exported into TigerPaw, Quickbooks and potentially mailchimp or another marketing tool - or have one built in which would allow us to do promotions and keep track of our customers. Users will then be able to checkout and pay and the monthly subscription then begins (we can customize the billing cycle) and customers can login to their account and upgrade (downgrade)/add-on hardware as they wish in the future. This can be a completely custom product if necessary or built off of an existing platform. This would also need to be skinnable for if we ever change our design - as well as to incorporate our existing designs. All the other standard shopping cart requirements that exist out there would be required as well (if it's an industry standard to have it, we want it in there). NOTE: If you are bidding and recommending building this on-top of an EXISTING cart, please note that in your BID or PMB - otherwise we will assume a completely custom solution. We will own the final product. IGNORE BUDGET - While I want to be able to do this at the lowest cost possible, if I see the value in the job to be worth the bid price, I may award for that instead.